Recipient Organization
UNIV OF WISCONSIN
21 N PARK ST STE 6401
MADISON,WI 53715-1218
Performing Department
(N/A)
Non Technical Summary
This project will test the efficacy of promising new bioenergetic solutions to improve animal health and limit the transmission of harmful bacterial pathogens.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
The goal of this proposal is to test a new method for controlling food-born bacterial infections: encapsulate iron. Specifically, we will determine how encapsulated iron affects S. enterica growth, virulence, and competitive interactions with beneficial gut microbes using established in vitro cecal and intestinal models and next-generation sequencing methods. We will also evaluate the anti-Salmonella therapeutic efficacy of SQM on infected broiler chickens by tracking the growth and gene expression of S. enterica during key pre- and post-harvest stages.These studies will provide critical information for how functional feed supplements might be used as a weapon against S. enterica. More broadly, given the conserved nature of iron metabolism across bacteria, we expect these data and methods will carry applications for other pathogens beyond S. enterica and carry much-needed non-pharmacological solutions to combating antimicrobial resistance.
Project Methods
Our long-term objective is to develop, empirically parameterize, and refine a multi-scale modeling framework that integrates across the molecular, organismal, and population levels.This project will contribute practical solutions for improving food safety and security and reducing pathogen spillovers from livestock to humans and the environment. Poultry studies focused on iron-Salmonella interactions remain particularly limited.While studies in poultry eggs demonstrate the important role that iron plays in Salmonella dynamics, most of our understanding of iron and Salmonella pathogenesis comes from rodent and mammalian cell culture assays, but conclusions drawn from these studies may not effectively translate to avian systems due to key physiological and morphological differences that affect how pathogens interact with avian environments. Thus, new animal models are needed to fill gaps left by mammalian Salmonella models. Our project will address these gaps in knowledge by integrating molecular, organismal, and population-level processes to provide key information on critical, but overlooked, aspects of Salmonella establishment, growth, virulence, and transmission. Together, these data will allow us to make recommendations on feed modifications and their effects on Salmonella and poultry health, including the gut microbiome, which would substantially reduce pre-harvest Salmonella and serve as practical diagnostic tools.Aim 1: Determine how iron availability affects within-host processes. Using established in vitro models, we will test the net effects of iron availability through multiple, potentially conflicting pathways. We hypothesize the encapsulated iron reduces metabolic syndrome, inflammation, and 'leaky gut' syndrome in the host, support beneficial gut microbes to enable competitive exclusion of S. enterica, but could increase the expression of virulence factors which pathogens use to acquire iron.Our preliminary aerobic in vitro data demonstrate that encapsulated limits the growth of S. enterica. These results provide proof of concept that encapsulated iron differentially reduces S. enterica growth relative to standard iron sources in commercial poultry feed (e.g., iron sulfate). However, it is unclear whether these in vitro results will hold in the anaerobic avian gut, and when S. enterica is in competition with gut microbes. For example, if gut microbes are more sensitive to iron limitation than S. enterica, then the in vitro pattern could reverse due to encapsulated iron limiting competition. We will build on these results to obtain a more integrated view of how iron affects the establishment and maintenance of S. enterica in avian environments. We have developed a novel in vitro poultry intestine-cecal model conducted in an anaerobic Coy Glove Box. Based on our previously published methods, this in vitro model allows us to determine encapsulated iron's impact on Salmonella growth and virulence in the presence of intestinal and cecal microbiota -- without the complex interactions of the host immune system.With this assay, we can track multiple variables simultaneously, reduce costs and time constraints by using a limited number of animals: ceca and intestines are collected from abattoirs, reducing the live animals required by 90%. Additionally, we can collect time-series data of these within-host interactions without causing undue stress to live animals. Thus, this in vitro model allows us to track key processes in the life cycle of Salmonella pathogenesis under different dietary conditions while reducing the logistical and welfare concerns of tracking infections in live birds. Using our established in vitro models combined with RT-PCR and Salmonella whole genome sequencing, we will test a series of interrelated hypotheses:Aim 1 H1: Encapsulated iron supports beneficial gut microbes that can outcompete S. enterica.Aim 1 H2: Encapsulated reduces excess free iron available to S. enterica.Aim 1 H3: Encapsulated iron reduces S. enterica growth rates and load.Aim 1 H4: Encapsulated iron reduces the expression of energetically costly traits that confer drug resistance (e.g., efflux pumps, plasmid acquisition).Aim 1 H5: Encapsulated iron increases expression of virulence factors that enable the pathogen to steal iron from the host and maintain iron homeostasis.Together, the relative influence of factors in H1-H5 (along with gut inflammation and permeability) will govern epidemiological and evolutionary effects of iron on S. enterica (future directions).Together, data from Aim 1 will provide key insight into the effects of iron on S. enterica via multiple, potentially interrelated pathways that operate at the molecular and cellular levels. The resulting time-series data on within-host processes are critical to developing and parameterizing multi-scale epidemiological and evolutionary models (future directions).All results will be analyzed using generalized linear models and generalized linear mixed effects models.Expected Outcomes & Relationship to Program Area Priorities: Do current dietary approaches over supply iron resulting in inflammation and fueling pathogen growth? Does withholding iron induce metabolic stress in S. enterica and lead to unintended increases in virulence genes? Does iron bioavailability significantly reduce S. enterica load in pre- and post-harvest poultry? By addressing these questions, this basic research project will help improve animal health, nutrition, and food safety, and the ability of the US industry to produce high quality poultry products more profitably and sustainably. By testing the novel applications of an existing, FDA-approved functional feed supplements, this proposed study will advance efforts to develop more integrated, nutrition-based interventions to combatting food-borne infections as well as antimicrobial resistance. By developing theory to improve our understanding of disease transmission and pathogen evolution, this proposal addresses multiple NSF goals and NIFA foundation priority Food Safety and Defense to promote research that sustains the competitiveness and long-term sustainability of US agriculture and fosters consumer trust. Finally, this project will improve our understanding of transmission dynamics in poultry systems, which are major culprits of pathogen spillovers to humans and the environment and also harbor and transmit genes that confer antimicrobial resistance. More broadly, this project will improve our understanding of the ecological and evolutionary factors that govern disease transmission, which is critical for managing disease outbreaks and for predicting and responding to future disease emergence and spillovers from livestock and wildlife to humans.